Optical scanning apparatus and image forming apparatus including optical scanning apparatus
At the time of forming an image, a rise in a temperature of a drive motor generates distortion in a bottom of a optical box of an optical scanning apparatus. If an opening is formed on the optical box to release heat, the optical box becomes easily distorted. To solve such a problem, according to the present invention, the optical scanning apparatus includes a rib which crosses over the opening formed at the bottom of the optical box.
Latest Canon Patents:
- Wireless communication apparatus, method of controlling the apparatus, and non-transitory computer-readable storage medium
- Information processing apparatus capable of preventing damage and loss of audit log when attack due to unauthorized access is detected, control method for information processing apparatus, and storage medium
- Communication apparatus, control method, and storage medium
- Adaptive loop filter
- Image reading device having a reading unit that includes a position reference
1. Field of the Invention
The present disclosure relates to an optical scanning apparatus and an image forming apparatus including the optical scanning apparatus.
2. Description of the Related Art
An image forming apparatus employing an electrophotographic method, such as a laser beam printer or a copying machine, includes an optical scanning apparatus which emits a light beam for exposing a photosensitive member. The image forming apparatus forms an electrostatic latent image on the photosensitive member using the light beam emitted from the optical scanning apparatus. The image forming apparatus then develops the electrostatic latent image using toner and forms an image.
When the image forming apparatus forms an image, the polygon mirror 1302 is rotationally driven by a drive motor. In general, the drive motor rotates at high speed, i.e., at 20,000 rpm to 40,000 rpm, so that temperature of the drive motor rises by 15° C. or more after a few minutes from starting to be driven. Temperature distribution is thus generated inside the housing 1306 due to heat generated by the drive motor becoming driven. The heat distribution causes uneven deformation of the housing 1306 to generate distortion.
In particular, since an amount of rise in temperature is greater in a portion where the drive motor is disposed as compared to other portions, an amount of deformation of the portion where the drive motor is disposed becomes relatively larger. As a result, the housing 1306 sags at a bottom to be basin-like shape with the drive motor as a center, as illustrated in
In response to the above problem, Japanese Patent Application Laid-Open No. 2009-198890 discusses an optical scanning apparatus in which an opening is formed in the vicinity of the drive motor to allow the housing to be capable of ventilation between inside and outside the housing. By forming an opening, the heat inside the housing is released, so that deformation of the housing can be suppressed.
The optical scanning apparatus discussed in Japanese Patent Application Laid-Open No. 2009-198890 is capable of reducing heat deformation by forming the opening. However, strength (i.e., rigidity) of a peripheral portion of the opening is lowered by forming the opening.
Referring to
According to an aspect of the present disclosure, An optical scanning apparatus comprising: a light source to emit a light beam; a rotational polygon mirror configured to deflect the light beam so the deflected light beam scans the a photosensitive member; a motor configured to rotationally drive the rotational polygonal mirror; and an optical box in which the rotational polygon mirror and the drive motor are disposed, wherein the optical box includes an opening and a connecting member configured to cross over the opening.
Further features and aspects will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the disclosure and, together with the description, serve to explain the principles disclosed herein.
Various exemplary embodiments, features, and aspects of the disclosure will be described in detail below with reference to the drawings.
The first exemplary embodiment will be described below.
When the image forming apparatus forms an image, the charging apparatus 108Y charges a surface of the photosensitive drum 107Y. An optical scanning apparatus 103 to be described below then exposes the charged photosensitive drum 107Y, so that the electrostatic latent image is formed on the photosensitive drum 107Y. The electrostatic latent image is made a visible image (developed) by yellow toner supplied from the developing apparatus 109Y.
Each of the image forming units 102M, 102C, and 102Bk similarly includes photosensitive drums 107M, 107C, and 107Bk, charging apparatuses 108M, 108C, and 108Bk, and developing apparatuses 109M, 109C, and 109Bk respectively. Functions of each of the elements are similar to those of the elements included in the image forming unit 102Y.
The toner image formed on the photosensitive drum in each image forming unit is transferred from the photosensitive drum to an intermediate transfer belt 105 at a primary transfer portions (i.e., Ty, Tm, Tc, and Tbk). The toner images transferred to the intermediate transfer belt 105 are then collectively transferred to a recording sheet conveyed from the sheet feed unit 101 to a secondary transfer unit T2. The recording sheet on which the toner images are transferred is conveyed to a fixing apparatus 106 which heat-fixes the toner image on the recording sheet 106. The recording sheet on which the fixing apparatus 106 has performed the fixing process is discharged to outside the image forming apparatus.
Next, the optical scanning apparatus will be described below. The optical scanning apparatus 103 exposes the photosensitive drums 107Y and 107M included in the image forming units 102Y and 102M, and an optical scanning apparatus 104 exposes the photosensitive drums 107C and 107Bk included in the image forming units 102C and 102Bk. Each photosensitive drum is exposed to the light beam, so that the electrostatic latent image is formed on the surface thereof.
Since the optical scanning apparatuses 103 and 104 are similarly configured, the optical scanning apparatus 103 will be described below as an example.
Referring to
Further, the optical scanning apparatus 103 includes a light source 208 which emits the light beam to which the photosensitive drum 107Y is exposed. The light beam emitted from the light source 208 is converted to a parallel light flux by a collimator lens 209 and becomes convergent light by a cylindrical lens 210 disposed immediately after the collimator lens 209. The cylindrical lens 210 has the refractive power to converge the light flux in the direction corresponding to the sub-scanning direction of the photosensitive drum 107Y (i.e., the rotational direction of the photosensitive drum 107Y). The light beam passing through the cylindrical lens 210 is formed into a predetermined shape by a diaphragm 211 and linearly-focused on the reflection surface of the polygon mirror 205, i.e., the rotational polygon mirror.
Referring to
The polygon mirror 205, the drive motor 218, the various lenses, and the reflection mirrors are contained inside a housing 219 (an optical box). The housing 219 is formed of a material which has been reinforced by mixing glass fiber in polyphenylene ether (PPE) and polystyrene (PS) resin.
As described above, the temperature in the vicinity of the polygon mirror 205 rises by 15° C. or more after a few minutes from when the drive motor has started rotating. Since the housing 219 is formed of resin, it is easily thermally-deformed. Particularly inside the optical scanning apparatus, the optical members such as the polygon mirror 205, various lenses, and the reflection mirrors are contained, so that the heat generated from the drive motor 218 is not uniformly diffused in the housing 219. As a result, when the image forming apparatus forms an image, heat distribution is generated in the housing 219.
In particular, the amount of a rise in temperature becomes greater in the peripheral portion of the polygon mirror 205 as compared to portions other than the peripheral portion (i.e., outside the peripheral portion). An amount of thermal deformation thus relatively increases in the peripheral portion, and basin-like shape deformation is generated in the bottom of the housing 219 as illustrated in
If the bottom becomes deformed to be basin-like shape, relative positional relations between the optical members become deformed, so that the optical path of the light beam is changed. As a result, the light beam is not focused on a desired position on the photosensitive drum. For example, the orientations of the reflection mirrors 214 and 216 greatly affect the optical path. If an angle in which each of the reflection mirrors 214 and 216 is positioned is changed by several minutes, an image forming position of the light beam on the photosensitive drum becomes displaced in the sub-scanning direction by 40 to 50 μm.
When the image forming apparatus forms the image by superimposing four color toner images, the above-described displacement of the image forming position of the light beam is visualized as color mis-registration and causes image quality deterioration. In particular, according to the present exemplary embodiment, the image forming apparatus employs the optical scanning apparatus that causes a plurality of light beams to scan in two directions opposing each other across the polygon mirror 205. The deformation of the housing 219 causes an irradiation position to be changed symmetrically. A relative amount of color mis-registration thus doubles to 80 to 100 μm.
According to the present exemplary embodiment, an opening is formed in the housing 219 of the optical scanning apparatus to release the heat inside the housing 219 generated by the temperature rise caused by the polygon mirror 205. Further, according to the present exemplary embodiment, reinforcement unit (reinforcement member, i.e., a connecting unit (member)) is disposed in the optical scanning apparatus for securing rigidity in the peripheral portion of the opening which has been reduced by forming the opening.
The opening will be described below.
Referring to
Referring to
As a result, air inside the housing 219 is released to outside the housing 219, and the air outside the housing 219 enters the housing 219 through the gap H2 formed between the housing 219 and the bearing 218a. The heat inside the housing 219 is thus released by the air inside the housing 219 being released to the outside. Further, the housing 219 and the optical members disposed inside the housing 219 are cooled by the air outside the housing 219 (i.e., the air which is relatively cooler as compared to inside the housing 219) entering the housing 219. Furthermore, an air layer is formed between the bearing 218a and an edge of the opening H1 by having the gap H2, so that it becomes difficult for the heat to be transferred from the bearing 218a to the edge of the opening H1 (i.e., the bottom of the housing 219). It thus prevents the housing 219 to be locally deformed due to heat, and distortion of the housing 219 can be reduced.
According to the present exemplary embodiment, the opening H1 is formed in the vicinity of the drive motor 218. However, the location of the opening H1 is not limited to the above. A similar result as described above can be expected by forming the opening H1 in a location corresponding to the area in which the temperature becomes relatively high in the housing 219.
According to the present exemplary embodiment, the bearing 218a of the drive motor 218 is inserted into the opening H1, so that the temperature around the opening greatly rises as compared to other areas in the housing 219. Since the edge portion of the opening H1 is a free end, it can be easily deformed by heat. Basin-like shape deformation may thus be generated in the housing 219 as illustrated in
To solve such a problem, according to the present exemplary embodiment, the rib, i.e., the reinforcement unit, is disposed in the optical scanning apparatus to secure the rigidity (i.e., strength) of the peripheral portion of the opening H1. As illustrated in
The reinforcement units will be described in detail below with reference to
Referring to
An engagement portion to which the bearing 218a is to be engaged will be described below with reference to
Dimensions of the ribs will be described below with reference to
The effect acquired according to the present exemplary embodiment will be described below.
Referring to
As described above, the opening H1 is formed to be capable of ventilation between inside and outside the housing 219. The rigidity of the housing 219 in the peripheral portion of the opening H1 which has been lowered by formation of the opening H1 is secured by disposing the ribs which cross over or traverse the opening H1. Generation of heat deformation of the housing 219 when the drive motor 218 is driven can thus be reduced.
The second exemplary embodiment will be described below. According to the first exemplary embodiment, the opening H1, which is capable of ventilation, is formed between the housing 219 and the bearing 218a in the optical scanning apparatus. However, according to the first exemplary embodiment, dust may enter the housing 219 via the opening H1. According to the present exemplary embodiment, the opening H1 is closed by a dust preventing seal to improve dust prevention as compared to the first exemplary embodiment.
As described above, the rigidity of the peripheral portion of the opening H1 can be increased by disposing the rib 1201, which connects to the ribs 220a and 220b and surrounds the opening H1. Further, the dust can be prevented from entering the housing by attaching the dust preventing seal 1202 on the rib 1201 whose height from the bottom surface of the housing is higher than that of the ribs 220a and 220b.
The shape of the ribs are not limited to the shapes illustrated in
Further, referring to
Aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiments, and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiments. For this purpose, the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (e.g., computer-readable medium). In such a case, the system or apparatus, and the recording medium where the program is stored, are included as being within the scope of the present invention.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions.
This application claims priority from Japanese Patent Application No. 2011-094156 filed Apr. 20, 2011 and Japanese Patent Application No. 2012-029865 filed Feb. 14, 2012, each of which is hereby incorporated by reference herein in their entirety.
Claims
1. An optical scanning apparatus comprising:
- a light source to emit a light beam;
- a rotational polygon mirror configured to deflect the light beam so the deflected light beam scans a photosensitive member;
- a motor configured to drive the rotational polygonal mirror;
- a bearing configured to bear a rotational shaft of the motor;
- an optical box on which an opening is formed and in which the rotational polygon mirror, the motor and the bearing are disposed, the bearing being inserted into the opening, and a gap being formed between the bearing and the optical box into which the bearing is inserted; and
- a connecting portion integral with the optical box and extending across the opening, wherein a portion of the connecting portion that extends across the opening is opposed to an end face of the bearing.
2. The optical scanning apparatus according to claim 1, wherein the optical box includes an engagement portion to be engaged with the bearing, and wherein the engagement portion is disposed integrally with the connecting portion and the optical box.
3. An image forming apparatus comprising:
- a photosensitive member;
- the optical scanning apparatus according to claim 2, the optical scanning apparatus configured to form an electrostatic latent image on the photosensitive member by scanning the photosensitive member with the light beam reflected by the rotational polygon mirror; and
- a developing unit configured to develop as a toner image the electrostatic latent image formed on the photosensitive member.
4. The optical scanning apparatus according to claim 1, wherein the connecting portion intersects on an extended line of the rotational shaft of the motor.
5. The optical scanning apparatus according to claim 1, further comprising a fixing unit configured to fix the rotational polygon mirror to a predetermined surface inside the optical box wherein the connecting portion extends from an external surface of the optical box, which is a back side of the predetermined surface.
6. The optical scanning apparatus according to claim 5, further comprising a reinforcement portion extending from the external surface of the optical box and configured to surround the opening, wherein the connecting portion and the reinforcement portion are integrally connected.
7. The optical scanning apparatus according to claim 6, wherein a height of the reinforcement portion from the external surface is higher than a height of the connecting portion from the external surface, and wherein a dust preventing seal is attached to the reinforcement portion and configured to prevent dust from entering the optical box from the opening.
8. The optical scanning apparatus according to claim 1, wherein the connecting portion is formed on an inner periphery of the reinforcement portion.
9. The optical scanning apparatus according to claim 6, further comprising a seal attached to the reinforcement portion.
10. The optical scanning apparatus according to claim 1, wherein an aperture is formed on the connecting portion.
11. The optical scanning apparatus according to claim 1, wherein the bearing is positioned in the opening.
12. The optical scanning apparatus according to claim 1, wherein the rotational polygon mirror is configured to reflect a first light beam emitted from a first light source in a first direction and reflect a second light beam emitted from a second light source in a second direction different from the first direction.
13. The optical scanning apparatus according to claim 1, wherein the connecting portion is fixed to an external surface of the optical box in such a way that the connecting portion connects edges of the opening.
14. The optical scanning apparatus according to claim 1, wherein the portion of the connecting portion extending across the opening engages with the end face of the bearing.
15. The optical scanning apparatus according to claim 1, further comprising at least two connecting portions extending across the opening, wherein a portion of each connecting portion that extends across the opening is opposed to the end face of the bearing.
16. The optical scanning apparatus according to claim 15, wherein the at least two connecting portions intersect with each other.
17. An optical scanning apparatus comprising:
- a light source to emit a light beam;
- a rotational polygon mirror configured to deflect the light beam so the deflected light beam scans a photosensitive member;
- a motor configured to drive the rotational polygonal mirror;
- a bearing configured to bear a rotational shaft of the motor;
- an optical box on which an opening is formed and in which the rotational polygon mirror, the motor and the bearing are disposed, the bearing being inserted into the opening, and a gap being formed between the bearing and the optical box into which the bearing is inserted; and
- a connecting portion disposed integrally with the optical box and arranged across the opening, the connecting portion arranged opposed to an end face of the bearing.
5357272 | October 18, 1994 | Watanabe et al. |
7471433 | December 30, 2008 | Shima et al. |
20020051635 | May 2, 2002 | Morofuji |
20040056963 | March 25, 2004 | Ishikawa |
1142155 | February 1997 | CN |
1920689 | February 2007 | CN |
1932586 | March 2007 | CN |
08278460 | October 1996 | JP |
2003-307762 | October 2003 | JP |
2006010814 | January 2006 | JP |
2008-003327 | January 2008 | JP |
2009-198890 | September 2009 | JP |
Type: Grant
Filed: Apr 2, 2012
Date of Patent: Sep 9, 2014
Patent Publication Number: 20120269551
Assignee: Canon Kabushiki Kaisha (Tokyo)
Inventor: Hitoshi Iwai (Abiko)
Primary Examiner: Hai C Pham
Application Number: 13/437,300